1. Field of the Invention
The present invention relates to a surface light source device and a liquid crystal display apparatus having the surface light source device. More particularly, the present invention relates to a surface light source device having an electrode to which a discharge voltage is applied and a liquid crystal display apparatus having the surface light source device.
2. Discussion of the Background
Generally, a liquid crystal display apparatus is a flat panel display apparatus that uses liquid crystals to display images. It has various advantages, including it may be small and lightweight. Further, since it does not consume a lot of power, it is widely applied to various electronic instruments.
The liquid crystal display apparatus requires a light source since its display panel is not self-emissive.
A tubular-shaped cold cathode fluorescent lamp is often used for the liquid crystal display apparatus' light source. In this case, the liquid crystal display apparatus may be broadly classified as an edge illumination type or a direct illumination type. In the edge illumination type, the light source is positioned adjacent to a side surface of a transparent light guide plate, and the light source's light reflects from the light guide plate and is applied to the liquid crystal display panel. In the direct illumination type, the light source is disposed under the liquid crystal display panel, a diffusing plate is disposed between the light source and the panel, and a reflecting plate is disposed under the light source. Therefore, before the light is applied to the liquid crystal display panel, the reflecting plate reflects it, and the diffusing plate diffuses it.
However, since the optical member, (e.g. the light guide plate, the diffusing plate, etc.) may induce light loss, this decreases the liquid crystal display apparatus' light efficiency. Furthermore, the apparatus' manufacturing cost may increase and its brightness uniformity may deteriorate.
Hence, a surface light source device emitting a planar light has been developed to reduce manufacturing costs and enhance brightness uniformity. Generally, the surface light source device may include a light source body having a plurality of adjacent discharge spaces and an electrode formed at each end of the light source body to apply a discharge voltage to it. The discharge spaces may be internally connected to each other so discharge gas may be uniformly maintained in each of them. Applying the discharge voltage to an electrode generates a plasma discharge in the discharge spaces so that the surface light source device emits light.
However, mercury ions may concentrate in a specific region, thereby blackening the region due to an electric potential difference, a geometrical shape of the light source body, or the like. Consequently, uniformity of the light from the surface light source device may deteriorate, and the lifetime of the surface light source device may decrease.